如何旋轉圓周上的物體？

Question

我創建了一個在oepnGL java中繪製圓的函數，我想在圓的圓周上旋轉另一個圓？

這是我創建圓的函數，如何改變它在圓周上繪製圓？

例如創建一個新的圓作爲第一個圓的中心座標點？

private void rotateAroundOz(GL2 gl, int r, double cx, double cy) { 
     int step = 1; 

     gl.glLineWidth(5); 
     gl.glBegin(GL.GL_LINE_LOOP); 
      for (int i=0; i<360; i+=step) { 
       gl.glColor3d(1, 0, 0); 
       gl.glVertex2d(cx + r * Math.cos(Math.toRadians(i)), cy + r * Math.sin(Math.toRadians(i))); 
      } 
     gl.glEnd(); 
    } 

Answer 1

你必須使用你從

cx + r * Math.cos(Math.toRadians(i)), cy + r * Math.sin(Math.toRadians(i))

// This is the attributes of the invisible circle: "PositionCircle" 
//that will gives you the circumference 
float positionCircle_Radius = 1.0; 
float positionCircle_CenterX = 0.0; 
float positionCircle_CenterY = 0.0; 

// This is actually the circle that you want to draw from the 
// "PositionCircle" 
int positionOnCircumferenceInDegrees = 90; 
float drawnCircle_Radius = 2.0; 
float drawnCircle_CenterX = positionCircle_CenterX + positionCircle_Radius * Math.cos(Math.toRadians(positionOnCircumferenceInDegrees)); 
float drawnCircle_CenterY = positionCircle_CenterY + positionCircle_Radius * Math.sin(Math.toRadians(positionOnCircumferenceInDegrees)); 

rotateAroundOz(gl, drawnCircle_Radius, drawnCircle_CenterX, drawnCircle_CenterY) 

計算位置，以便您可以添加positionOnCircumferenceInDegrees和drawnCircle_Radius爲參數，爲您的新功能來畫一個圓（與rotateAroundOz()） 。

（這是我對SO的第一個迴應：希望它能被理解！）